A lead frame for semiconductor devices is used to mount a semiconductor device on a substrate or the like. Japanese Laid-Open Patent Publication Nos. 2004-349497 and 2004-332105 describe lead frames in the related art. In a semiconductor device, a semiconductor element is mounted on a lead frame and encapsulated together with the lead frame in a resin material. In this case, for example, the surface of the lead frame is roughened to increase the adhesion between the lead frame and the resin material.